A hard-disk drive (HDD) is a non-volatile storage device that is housed in a protective enclosure and stores digitally encoded data on one or more circular disks having magnetic surfaces (a disk may also be referred to as a platter). When an HDD is in operation, each magnetic-recording disk is rapidly rotated by a spindle system. Data is read from and written to a magnetic-recording disk using a read/write head which is positioned over a specific location of a disk by an actuator.
A read/write head uses a magnetic field to read data from and write data to the surface of a magnetic-recording disk. As a magnetic dipole field decreases rapidly with distance from a magnetic pole, the distance between a read/write head, which is housed in a slider, and the surface of a magnetic-recording disk must be tightly controlled. An actuator relies in part on a suspension's force on the slider and on the aerodynamic characteristics of the slider air bearing surface (ABS) to provide the proper distance between the read/write head and the surface of the magnetic-recording disk (the “flying height”) while the magnetic-recording disk rotates. A slider therefore is said to “fly” over the surface of the magnetic-recording disk.
As recording tracks in HDDs become narrower and narrower, there is a need for more accurate and sustainable head positioning. One of the main factors impairing accurate positioning is airflow caused by rotation of the disk which, when striking the arm supporting the head slider, causes the arm to vibrate and head positioning to suffer. Thus, the manner in which airflow disturbances are suppressed in order to restrict arm vibration is an important factor in improving positioning accuracy.
There is a known approach, referred to as a bypass channel, in which airflow that would otherwise strike the arm is diverted. Such a system is implemented using an airflow channel such that airflow flows outside the area of the disk, bypassing the arm. The airflow enters the channel upstream of the arm (e.g., at a 9 o'clock position on the disk) and returns to inside the disk area downstream of the arm (e.g., at a 3 o'clock position on the disk).
A bypass channel can be readily implemented into an HDD system in which the disk diameter is considerably smaller than the transverse width of the HDD base. However, in HDD systems in which the diameter of the disk is comparable with the transverse width of the base, it is difficult to maintain an adequate width for the flow channel due to space constraints within the HDD, and the effect of the fluid diversion action is inhibited. Furthermore, most of the air (or other gas) within the HDD is diverted with use of the known technologies, thereby making it difficult to cool the coil of the voice coil actuator. Thus, there is a risk that the coil temperature increases beyond its effective operating limit and, consequently, inhibits the actuator's seek performance.